Airplane



Dec. 23, 1930. 1.. STEARMAN AIRPLANE Filed May 6, 1929 8 Sheets-Sheet 2 R O T N E V m Dec. 23, 1930. STEARMAN A .[RPLANE] Filed May 6, 1929 v 8 Sheets-Sheet 3 5 INVENTOR AT RNEY De c. 23, 1930. L. STEARMAN A .[RPLANE Filed May 6, 1929 8 Sheets-Sheet INVENTOR BY X AT $RIIQ ec. 23, 1930. STEARMAN 1,786,136

AIRPLANE Filed May 6, 1929 8 Sheets-Sheet 5 5 INVENTOR ATTzRr JEY DEC. 23, 1930. S E MAN 1,786,136

AIRPLANE Filed May 6, 1929 8 Sheets-Sheet 6 5 INVENTOF? ATT RNEY Dec. 23, 1930. I L. STEAR AAN AIRPLANE Filed May 6, 1929 8 Sheets-Sheet '7 INVENTOF:

Dec. 23, 1930.

L. STEARMAN A IRPLANE Filed May 6, 1929 8 Sheets-Sheet 8 Patented Dec. 23, 1936 UNITED STATES PATENT OFFICE LLOYD STEARMAN, OF WIOHITA, KANSAS, ASSIGNOR TO THE STEARMAN AIRCRAFT COMPANY, INC., 01: WICHITA, KANSAS, A CORPORATION OF KANSAS AIRPLANE Application filed May 6,

The present invention relates to the improvement of airplanes generally, but more particularly the objects are to improve the landing gear and fuselage structure, to provide greater comfort and safety for the pilot. and passenger, to enable the quick conver sion when desired, from passenger to loadcarrying purposes and to improve the control and stability of the machine.

Further desirable objects and the novel features of construction, combinations and relations of parts by which all such objects are attained will appear as the specification proceeds.

The drawings accompanying and forming part of the specification illustrate a practical commercial embodiment of the'invention, but it will be understood that various modifications and changes as regards this present disclosure may be made without departure from the true spirit and broad scope of the invention.

Fig. 1 is a broken plan view and Fig. 2 is a side elevation of the machine; Figs. 3, 4 and 5 are side, broken plan and front views respectively of the skeleton fuselage and landing gear; Fig. 3 is an enlarged broken crosssectional view of the fuselage frame as on substantially the plane of line 66 Fig. 3 and illustrating particularly the vertical adjustment features of the pilots seat; Fig. 7 is a broken sectional View on a plane at right angles to that of Fig. 6, as on substantially the plane of line 7-7 of Fig. 6; Fig. 8 is a broken plan view of the vertically adj ustable pilot seat construction; Figs. 9 and 10 are broken sectional longitudinal and plan views respectively of the tail skid construction; Figs. 11 and 12 are side and front views respectively of one of the shock absorbing wheel struts. with the fairing therefor shown in section: Fig. 13 is an enlarged broken sectional detailed view of the cylinder and piston hydraulic portion of the shock strut; Fig. 14 is a broken plan of the forward central portion of the ship; Fig. 15 is a broken crosssectional view as on substantially the plane of line 15-15 Fig. 14: Figs. 16 and 17 are broken sectional details illustrating the change from a roll and wind shield toa hat-ch cover for converting the forward compartment from passenger to load-carrying purposes; Fig. 18 is a skeleton view of the differential aileron, the elevator and the rudder control mechanism.

The machine chosen for illustration is a two-place biplane constructed to enable the quick conversion of the passenger cockpit 25, Figs. 2 and 14 to a mail pit by the substitution of a suitable hatch cover 26, Fig. 17 for the ring 27 carrying the roll 28 and windshield 29, the ring and cover fitting inter-, changeably in the seat 30 about the cockpit opening 31 over studs 32 and removably held by the safety pin or wire 33. The roll or air cushion is shown as doubled over the edge of the ring and secured by bolts, rivets or other suitable fastenings 34, these same fastenings being utilized about the front to also fasten the windshield down in place over the top of the roll. By the construction described, the owner of the plane may quickly convert the forward cockpit from passenger to mailcarrying operations and the plane might be sent out from the factory for either use.

. To adapt the machine to carrying, taking off and landing with heavy loads in either of the uses described, the fuselage is rigidly braced and special landing gear is provided fore and aft, tied into the fuselage structure. The forward landing gear comprises in the present disclosure combination hydraulic and elastic shock struts spaced widely apart by outriggers standing out from the bottom of the frame and trussed to the top of the frame. In the front view, Fig. 5, the landing wheels 35 are shown carried by stub axles 36 on the outer ends of relatively long angled struts 37, which are pivoted at their inner ends at 38 to a bracket 39 fixed to the bottom forward portion of the frame substantially at the center transversely thereof. This pivot fitting is shown as attached to the front cross-bar 40 and as trussed by angled braces 41 extending from the fitting 11 into the upper corners of the frame. The w eel-carrying struts are braced by the rearwardly angled struts 42 pivoted. on the center line at the underside of the frame at 43, in line with the forward pivots 38.

The shock struts which are indicated generally at 44 are pivotally connected at the lower ends at 45 with the axles or aXle struts and pivotally connected at their upper ends at 46 with the supports 47 standing out from the sides of the frame. These supports are shown in the form of extensions of the lower front cross-bar 40 and they are indicated as trussed by braces 48 extending from the outer fittings 49 upwardly and inwardly to the upper longrons 50 of the frame. The angled )IHCBS 41 inside the frame and the angled braces 48 outside the frame form with the lower cross-bar and the extension struts 47 a double trussed system capable of safely carrying all shocks and strains and this construction places the shock struts in favorable position for the wide spacing of the landing wheels. In addition, the outboard struts 47 provide an anchorage for the brace wires 51 for the upper wings, Figs. 5 and 15, enabling said wires to be run at a better load-carrying angle than if they were tied in directly to the sides of the frame in accordance with customary practise. The same end fittings 49 which carry the upper pivots for the shock struts are shown here utilized for the fastening of these brace wires, they being equipped with eyes 52 receiving the end fastenings of the wires. It will be seen that the inwardly angled braces 48 enable the outstanding. struts 47 to carry this extra load of the wing braces.

Fore and aft bracing of the outstanding 'strut is effected in the illustration, Figs. 3 and 4, by substantially horizontal braces 148 extending angularly from the outer ends of the struts 47 back to the sides of the frame and continued inwardly at 149 substantially to the center of the frame. The truss 47 with its vertical and lateral braces 48 and 148 thus forms an outstanding substantially triangular support or tripod with two of its legs rooted in the bottom longron and the third leg connected with the upper longron and thus well capable of carrying the various shocks and loads to which it may be subjected.

The shock struts in the present disclosure consist each of a tubular piston 53, forming the upper member, pivoted in one of the outboard fittings 49 through the medium of a universal block 54 .and a cylinder 55 forming the lower member and pivoted at its lower end to a wheel strut, said two members constituting a hydraulic buffer to take the land ing or heavier shocks and being elastically connected to carry the lighter shocks. The

piston member is-shown in Fig. 13 as having a closed lower end at 56 with a bolt 57 therein having a through passage 58 with funnelorifice bolt. A suitable gland packing 60 is indicated where the tubular piston emerges from the upper end of the cylinder. The piston tube is shown as havin a pair of substantially parallel rods or tubes 61 attached to the upper end of the same by a cross head 62, said rods extending down to opposite sides of the cylinder and braced together at their lower ends by a cross-piece 63, the latter having a sliding fit in its intermediate portion over the barrel of the cylinder. For further guiding purposes, these side rods 61 are shown as having inwardly extended shoes 64 extending partly about the directly opposite side portions of the cylinder. These guides or shoes are located between the upper and lower cross-connected ends of theside rods and may ordinarily be free of c'onta'c't or have a light sliding fit with the cylinder barrel being designed to brace the barrel in a fore and aft direction to enable thelatter to work smoothly over the piston under extreme conditions. The elastic connection between the two members of the shock strut is provided in the present disclosure by a single length of elastic shock cord 65 made fast at its opposite ends by clamps 66 on the rearward side rod and laced in continuously extending fashion alternately over studs 67 and 68 on the side rods and cylinder respectively. This cord at each bend passes between a pair of the studs and so is confined vertically for stretching movement both up and down. Thus on lauding, the cord will be stretched by the upward movement of the cylinder into the upwardly angling bends indicated in Fig. ll and on leaving the ground. the cord, acting with the weight of the wheel will pull the cylinder down to draw the oil back into the bottom of the cylinder below the cup piston ready for the next landing. In landing. the hydraulic portion of the apparatus takes the first shock, the flow of oil and hence the first yielding action being determined by the size of the flow orifice 58.' After this first relief of shock, the elastic cord assumes the carrying load, acting as a resilient spring support while the machine is manoeuvring on the ground, the hydraulic end of the apparatus remaining however in reserve to automatically come into action for modifying the elastic support in case of any extreme or suddenly encountered shocks.

. T 0 reduce air resistance and at the same time afford mechanical protection, the elastic cord portion of the shock strut may be encased within a stream line boot or shell 69. The cylinder, piston and connected side rods line up fore and aft as indicated in Figs. 5 and 12 and brace each other in the direction of greatest strain. The hydraulic and the elastic absorber means act both singly. and jointly and at different times one supplementing the action of the other. In case of failure of either, the other is present to temporarily carry the load. The oil or other liquid may be entered through a fillin fitting in the upper end of the hollow piston and may be drained by removal of a plug 71, Fig. 12, in the lower end of the cylinder. The elastic cord is readily renewable by simply releasing the end clamps 66 and then lacing in a new length of shock cord and securing as before.

The tail skid is shown inFigs. 3, 9 and 10 as a skid shoe 72 detachably bolted on the lower end of an inclined post 73, which is pivoted horizontally at 74 to the lower end of an upright stud 7 5 journalled vertically in a bearing 76, the latter carrying a forwardly and upwardly angled tube 77 forming an anchorage for the elastic shock cord 78, which is laced thereover and about the upper end of the skid post. A guard 79 confines the cord lacings to the upper end of the post and a cable connector 80 between this guard and the anchor tube limits the stretching movement of the cord and acts as a safety holder in case of breakage of the cord.

In order that the entire tail skid assembly may be quickly mounted and unmounted as a unit, the same is shown as detachably secured by two bolts 81 clamping the flanged portions 82 on the back of the bearing sleeve 76, to the bosses or boxes 83 on the lower cross-frame bar 84. The upper end of the anchor bar is shown as entered in a sleeve or collar 85 carried by convergent struts 86 angled downwardly and forwardly from the upper longrons 50. The anchor post may have a sliding fit in the supporting collar 85, so that upon removal of the two bolts 81, the rearward end of the skid anchor may be dropped down and then pulled out of the sleeve 85, thus enabling the removal of the entire tail skid assembly as a single unit.

The tail skid constructed as described has freedomlior both vertical and lateral movements and the lacing of the cord has the effect of always pulling the skid back to the center line position. To save theframe in case of breakage of the tail skid, a small jury skid'plate 86, Fig. 3 may be extended from the bottom longrons 87 downwardly on an angle and beneath the foot of the rear frame upright 88.

In the machine here shown, the pilot seat 89 may be raised and lowered, for better vision in landing and take-oil or for greater comfort and ease in long distance flying, the same being shown for the purpose carried by upright tubes 90 sliding in upper and lower guide sleeves 91, 92 on the frame, it being automatically lifted to the desired elevation by a loop of shock cord 93 passed beneath the seat, Figs. 6, 7 and 8 and being latched in the desiredposition of adjustment by a spring pressed latch bolt 94 operating in the lateral guide extensions 95 of the lower guide sleeves- 92 and engaging in different openings 96 in the side rods of the seat. This latch rod is shown in Fig. 8 as rearwardly offset at 96 to extend to the rear of the right hand guide sleeve and as looped back upon itself at 97 to bring this end of the rod into the same plane with the opposite end, so as to operate in the right hand guide 95. This looped portion of the rod is shown as engaged by a forked lever 98 pivoted on the frame at 99 and having a handle 100 positioned to be readily reached by the pilot. When this handle is rocked upwardly to pull the rod to the right in Fig. 6 against the force of spring 101 and the ends of the rod are thereby disengaged from openings 96 in the uprights 90, the seat will rise, as permitted by the pilot, under the lifting force of the elastic cord 93 and when the desired elevation is attained, the handle may be released to permit the bolt to snap back into engagement with the nearest pair of keeper openings in the seat uprights. Thus, the pilot may quickly adjust the seat to a higher'level, for instance, for

Y securing greater vision in taking off or landing by simply pullin on the handle 100 and temporarily taking his weight oil the seat or he may lower the seat for greater relaxation and protection in long distance driving by pulling on the handle and permitting his weight to force the seat down to a lower level. Either adjustment may be readily effected without the necessity of shifting out of the seat or removing attention from the control of the ship.

The control system is illustrated particularly in Figs. 14 and 15 and 18 as comprising ailerons 102, 103 hinged in the upper wings at 104 and operated through dill'erential connections from the control stick 105. These differential connections are shown in the form of crank arms 106, 107 extending at downwardly divergent angles from the-main torque tube 108 and links 109. 110 extending in crossed relation upwardly to rocker arms 111, 112 respectively on the ends of the shaft extensions 113, 114 of ailerons 103 and 102. The stick is shown as pivoted transversely on the main torque tube at 115, so that it may tilt fore and aft, but will turn the torque tube when swung transversely. The angularity of the crank arms 106, 107 on the torque tube in the case illustrated, is such that for an equal movement of the stick one aileron will be turned up 15 while the opposite aileron will be turned down 22. The degree of differenti al however is governed by the relative angu' larity of the cranks, it being evident that with the down-turned cranks shown, the crank which is moving upwardy in travelling through the more effective are will impart a greater movement than the crank which is moving downwardly the same extent but through the lesser effective are.

Cables 116 are shown extending from the stick above its pivotal mounting 15 to the lower ends of the elevator rocking levers 117 and cables 118 from the lower end of the stick below the ivotal mounting to the upper ends of the roc ing levers to effect the desired elevator control.

The rudder 119 is shown controlled by cables 120 from stirrup levers 121 hingedly suspended in opposite sides of the pilots coc (pit.

The entire surface control system is thus made direct and simple and a desired differential aileron movement is attained by simple positive means. The two crank arms 106, 107 which are in the illustration extended on slight downward angles from the horizontal, may be made as a bell crank structure fixed .on the forward end of the main torque tube and complication is avoided and the action made positive by directly connecting these cranks or hell crank arms through the pushpull' links 109, 110 with the two shafts which rock the ailerons.

To facilitate entry to and exit from the forward cockpit, the latter is shown in Fig. 2 as having a side door 122 of generally triangular shape, with the peak of the triangle downwardly and with the hinges 123 in the forward downwardly inclined side of the triangle, so that the door will swing donwardly and forwardly as indicated in the dotted lines to pivot, out of the way of a person entering or leaving by standing on the lower wing. To allow for this door-way, a dip is provided in the left-hand side of the frame, where, as shown in Figs. 3 and 4, the upper longron is brought down at 124 between the upright braces 125 and joined with braces 126 angled upwardly to the notch of the V thus formed. The desired dip in the frame for the V door is thus roduced without weakening the frame at t is side.

The jury-skid is shown so located as to carry the tail load in the event of a breakage in the resiliently mounted tail skid and the latter in such event is prevented from tripping the machine by the inextensible movement-limiting cable connection. In flight, the pilot may lower his seat to the best position comfortable for driving by simply releasing the seat lock and bearing down to force the seat to the position of greatest comfort and protection. Conversely, for landing, or when greater vision is desired, the pilot may quickly trip the seat lock and 'permit the spring loop to lift the seat to the height where greater vision is obtained. Both adjustments are effected without diverting the pilots attention and only requiring the use of one hand to release the lOCl-I or latch. The differential control of the ailerons gives the ship a proper balance for banking and turning and this differential action is attained by simple, positive, direct connections. Similarly. the elevator action is direct, positive and safe, being free of any the center mounting at 83, Figs. 3, 4, 5, 9, 10.

Diagonal braces 150 extending convergently from the sides of the frame to the lower crossbar 151 which carries the pivotal, mount 43 for the drag struts 42 brace said cross-bar longitudinally of the frame and provide support for flooring in the passenger or mail-pit compartment. Rearwardly convcrgent struts 154; additionally brace this portion of the machine and provide flooring support in the pilots compartment.

lVhile the various features of the invention are particularly related to machines of the biplane type. as illustrated, it should be understood that they may be applied to monoplanes and other types of aircraft and it should further be understood that in view of the broad scope of the invention, the terms employed herein have been used in a descriptivc. rather than in a limiting sense, except for such limitations as may be required by the state of the prior art.

lVhat is claimed is:

1. In aircraft construction, a frame, struts extending outwardly from the sides of the frame at the bottom portion of the same, braces angled to carry vertical and horizontal loads on said outstanding struts and extending from the outer ends of said struts to the frame. landing gear attached to said outstanding struts and including shock struts pivoted at their upper ends to said outstanding struts, braces connecting the lower ends of said shock struts with the central portion ofthe frame and internal trusses within the frame between said central portion of the frame and points where the braces of the outstanding struts are connected with the frame.

2. As a new article of manufacture, a. fuselage frame for aircraft, comprising upper and lower lougcrons connected by uprights and upper and lower crossbars, one of said bottom. cross-bars having extensions beyond the lower longrons to form outboard landing. gear struts and braces extending angularly from the outer ends of said struts upwardly to the upper longerons and inwardly to the lower iongerons to brace said outboard struts .both vertically and horizontally.

As a new article of manufacture, a fuselage frame for aircraft, comprising upper and lower longrons connected by uprights and upper and, lower crossbars, one of said tillarly from the outer ends of said'struts upwardly to the upper longrons and inwardly to the lower longrons to brace said outboard struts both vertically and horizontally and braces extending convergently downward from the upper ends of said vertical outboard braces to the central portion of said cross-bar, said braced central portion of the cross-bar and the outboard extensions of the same carrying fittings to receive landing gear connections.

4. In aircraft landing gear, the combination with a fuselage having outboard landing struts projecting from the sides at the bottom of the fuselage, shock struts pivoted at their upper ends to said outboard struts, landing means pivoted to the lower ends of said shock struts, inwardly angled struts connected with said landing means and pivotally connected with the lower c'entral portion of the fuselage, rearwardly angled struts extending from said landing means to the lower central portion of the fuselage and inwardly angled braces extending from the outboard landing struts upwardly to the upper fuselage structure and from the outboard struts in a fore and aft direction to the lower fuselage struc ture.

5. In aircraft, a fuselage frame having ton and bottom longrons, rigid permanently attached landing gear struts projecting laterally from the lower longron structure, in

wardly angled compression struts extending from the outer ends of the landing gear struts to the upper longron structure, fore and aft braces extending from the outer ends of the landing gear struts to the lower longron structure, landing gear attached to the outer braced ends of said landing gear struts, inwardly and upwardly angled braces extending from said landing gear to the central intermediate portion of the fuselage frame, and

outwardly and upwardly divergent braces from the fiitermediate point of attachment of the last mentioned braces to the upper longron structure.

- 6. In aircraft, the combination of a fuselage frame, landing gear struts projecting laterally from the lower portion of the fuselage frame, inwardly angled braces extending from said laterally projecting struts to the upper portion of the fuselage frame, landing gear attached to said braced laterally projecting struts, inwardly and upwardly angled braces extending from said landing gear to the lower central portion of the fuselage frame and braces extending from the upper portion of the fuselage frame inwardly and downwardly to the intermediate central portion of the frame where said landing gear braces are attached.

lage frame, landing gear struts projecting laterally from the lower portion 0 the fuselage frame, inwardly angled braces extending from said laterally projecting struts to the upper portion of the fuselage frame, landing gear attached to said braced laterally projecting struts, inwardly and upwardly angled braces extending from said landing ear to the lower central portion of the fuse age frame, braces extending from the upper portion of the fuselage frame inwardly and downwardly to the intermediate central portion of the frame where said landing gear braces are attached, fore and aft braces extending from the laterally projecting struts to the lower portion of the fuselage frame and fore and aft bracing struts extending upwardly and inwardly from the landing gear to the intermediate central portion of the fuselage frame.

8. In aircraft, a fuselage frame, landing gear struts projecting substantially horizontally from the lower portion of said fuselage frame, angled braces extending from the outer ends of said horizontally projecting struts to the fuselage frame, wing braces anchored to the outer ends of said horizontally projecting struts and landing gear means connected with the outer ends of said horizontally proj ecting struts and with the lower central portion of the fuselage frame.

In testimony whereof I affix my signature. LLOYD STEARMAN.

7. In aircraft, the combination of a fuse- I 

